Endovascular delivery catheter assemblies are used to implant prosthetic devices, such as prosthetic heart valves, at locations inside the body that are not readily accessible by surgery or where access without invasive surgery is desirable. For example, aortic, mitral, tricuspid, and/or pulmonary prosthetic valves can be delivered to a treatment site using minimally invasive surgical techniques.
An introducer sheath can be used to safely introduce a delivery apparatus into a patient's vasculature. An introducer sheath generally has an elongated sleeve that is inserted into the patient's vasculature and a housing with one or more sealing valves that allows a delivery apparatus to be placed in fluid communication with the vasculature while preventing blood loss. A conventional introducer sheath typically requires a tubular loader to be inserted through the seals in the housing to provide an unobstructed path through the housing, thereby allowing a prosthetic device to be passed through the introducer sheath.
Certain approaches through the heart for mitral valve replacement can be particularly challenging for delivery of prosthetic mitral valves due to the sharp turns needed near the end of the introducer sheath. An example of a stent-mounted mitral valve prosthetic is described in U.S. Pat. No. 8,449,599, which is hereby incorporated herein by reference. FIG. 67 of the '599 patent (replicated herein as FIG. 1) illustrates delivery of a prosthetic mitral valve via a transseptal approach. More specifically, an incision is made in the atrial portion of a septum 30 for allowing access from a right atrium 26 to a left atrium 4. A sheath 2102 of a delivery catheter 2100 is inserted into the left atrium 4 and bent sharply in the direction of the mitral valve. Once in the left atrium 4, the distal end of the sheath 2102 is moved across the mitral annulus such that ventricular anchors 126 of the prosthetic valve 100 are positioned beyond the mitral leaflets 10, 12. The prosthetic valve is expelled from the distal end of the sheath 2102 using pusher shaft 2106.
Despite the improvements provided by the '599 patent, the sharp bend in the introducer sheath (prior to reaching the mitral valve) increases the difficulty of withdrawing the sheath relative to the pusher and mitral valve. The sheath has to be retracted backwards around two bends. Also, there is limited space in the heart chambers (left ventricle and left atrium) for relative movement of the introducer sheath and the deploying prosthetic mitral valve. The lack of space makes it difficult for the cardiologist to deliver the prosthetic mitral valve. Thus, there remains a need for improvements to delivery systems for prosthetic mitral valves, especially for transseptal approaches.